The objective of the proposed research is to gain insight into the control of transcription and processing of RNA in eucaryotes, particularly during development. I propose to investigate the characteristics of Drosophila hnRNA molecules which are precursors to mRNA, using heat shock to induce a specific set of transcripts. These molecules will be examined with regard to size, content or reiterated sequences and content of double-stranded regions to determine if they possess features in common which differentiate them from the total hnRNA populations. The small number of RNA transcripts and proteins which appear after heat shock indicate that it should be possible to identify and analyze the specific gene products. I therefore propose to isolate mutants in one of the regions activated by heat shock so that genetic tools can be enlisted to dissect aspects of eucaryotic gene regulation. Finally, I plan to analyze the appearance of different mRNA sequences during development of the embryo to obtain a basic understanding of the organization of transcription during eucaryotic development.